31 Seater Projects - Norms Buses - Monthly activity

31 December 2016
: I'm at the stage now where I am putting things back on the engine.
: I have come across a curious problem.
: Most of you will just put this under the useless info banner and not think about it anymore.
: Anyway, Some of the bolts that I have taken out of the engine and now putting back have been a little tough to do.
: I have up till now cleaning the bolts of dirt and rust etc.
: Generally cleaning them up and painting the heads.
: Because they have been a little hard I have been retapping some of the threads.
: Curiously when I used my tapping gauge to measure the thread the bolts have been falling between teeth per inch size.
: Specifically speaking 3/8" x 19TPI.
: There isn't such a size.
: I retapped the hole in one instance and the bolt and it was tough doing it.
: When I had finished and tried the bolt it didn't feel as tight as it had been.
: I know that bolts do stretch, but my understanding is that it happens in the course of the length and not in the area of the where the 2 threads bind together.
: It's like with modern cars when you take the head off for whatever reason you have to replace the head bolts because of the stretching.
: The bolts I am talking about are around 50mm long. Anyway, I thought I would share that with you.

: Mark Ellery
: They may have been an obscure engineering thread, there a huge number of them,
: used in one or a few applications only and unless you source original documentation most get adapted over time,
: very early motorcycles a very trouble some to restore to original

: Reply · 31 Dec 2016
: Norman Julian
: I have heard of some really strange things over the years but that one certainly falls into the bazaar category, Mark.
: In this situation I don't think it is the case.
: Most of them are OK. It's just some of them that my have come out of one area and a different bolt [the same size] goes back into
: a different position I have found this bazaar thing.
: It has been on the engine by the way. Where there is heat.
: Anyway I have stopped doing it.
: I cleaned up the thread the best way I could and put them back in and in most cases they are OK.

: Brian Musgrove
: I did my apprenticeship on British equipment and it was either whit worth or CT or cycle thread, I have seen this around electrical equipment

Norms Restoration - 31 Seater Projects

1952 AEC Regal III [2547]

2016

December Mechanical